Method and apparatus for poling polymer thin films

ABSTRACT

A poling apparatus for poling a polymer thin film formed on a workpiece carried by a workpiece carrier. The workpiece has multiple grounding electrodes, grounding pads located at its edges, and a polymer thin film including multiple areas each covering only one grounding electrode. The poling apparatus includes, in a poling chamber, a poling source generating a plasma, a shadow mask below the poling source, and a Z-elevator to raise the workpiece carrier toward the shadow mask and poling source. When the workpiece in the workpiece carrier is raised to contact the underside of the shadow mask, multiple openings of the shadow mask expose only the corresponding multiple thin film areas of the workpiece to the plasma; meanwhile, conductive grounding terminals on the underside of the shadow mask electrically connect the grounding pads of the workpiece with carrier electrodes on the workpiece carrier, to ground the workpiece.

BACKGROUND OF THE INVENTION Field of the Invention

The embodiment of this disclosure relates to a poling technology thatpolarizes polymer thin films and, in particular, relates to a polingchamber, a work piece used with the poling chamber, and related polingmethods.

Description of Related Art

After crystallization by annealing, materials like PVDF (polyvinylidenedifluoride) and their co-polymers (PVDF-TrFE, for example) need to bepolarized (or poled) in order to re-align their randomly orientedmolecular electrical dipoles along certain desired direction. Thispolarization or poling process transforms the polymer materials topossess certain electroactive properties. They may includepiezoelectric, pyroelectric or others desired properties. It is theseproperties that form the foundations for many polymer-based transducers,sensors, actuators and memories.

To carry out the poling process for the polymer thin film, a fairlystrong electric field is established, for instance, perpendicular to thesurfaces of the thin film. The electric field may be created by applyinghigh voltages across conductive electrodes deposited on the two oppositesurfaces of the thin film (see FIG. 9). This method is referred to asdirect poling. In another method called plasma poling, the electricfield is induced by a layer of dense electric charge which isdynamically formed by like charged species (e.g., electrons, negativeions) out of a plasma that is generated by ionized gas inside a closedchamber.

The polarization of the film is a significant part of the processing ofthin-film materials. The goal is to re-align randomly oriented molecularelectrical dipoles within a polymer thin film along the desireddirection (such as the direction of the applied poling field). Thispolarization or poling process transforms the polymer materials topossess specific electro-active properties. The poling process of thepolymer thin films is slow as it can only polarize one polymer thin filmat a time. Accordingly, there is a need in technology for providing afast poling process.

In mass producing electroactive polymer thin film-based devices(sensors, for example), it is desirable to form selected areas (oftenpatterned) on the thin film to become electroactive sensing pads, the socalled “active areas” in sensor technology. One method is to firstdeposit a blanket polymer thin film over the entire substrate, then toplasma pole the blanket thin film as a whole, and finally to formdesired active areas using conventional patterning techniques whereunwanted polymer thin film is removed outside of the active areas (e.g.,done by photolithography followed by wet chemical etch or plasma dryetch). An alternative method is to selectively deposit (e.g., byselective slit coating, screen printing, etc.) the polymer thin film ona substrate to define the active areas without resort tophotolithography and subsequent etch processes; a matching shadow maskof patterned openings is then used to cover the substrate; the activeareas of the thin film are formed by exposing those defined areasthrough the openings to the electrical charge flux in a plasma polingprocess. For making sensors of larger than 1×1 millimeter in dimensions,it is often advantageous to apply the alternative method without usingphotolithography. This is because it does not rely on expensiveprocesses such as photolithography, wet- or dry-etch to pattern thepolymer thin films to form the active areas.

SUMMARY

Plasma poling apparatus can polarize electrical dipoles and displaceother electrically charged constituents (electrons, ions, etc.) insidepolymer materials to transform those materials into electroactive ones.Embodiments of this invention provide a method and associated apparatusto implement mass production process for plasma poling of polymer thinfilms over large area workpiece. The plasma poling method and apparatusare applicable to fabrication of electroactive polymer-based sensors,actuators, transducers, memory devices, touch control panels, pressuresensors, temperature sensors, infrared imaging sensors, fingerprintsensors, active cooling devices, as well as electric energy storagedevices. For higher speed, more uniform and higher yield poling process,embodiments of this invention provide a grounding method designed in theapparatus. A modularized and arrayed approach is also disclosed forconstructing large area poling sources, which are key for large areapoling apparatus to achieve uniform and damage-free process.

The embodiments of the present disclosure provides a type of polingchamber to achieve the fast polarization of polymer thin films. Variousembodiments and aspects of present invention provide a poling chamber, acarrier platform, and a workpiece for poling polymer thin film, andrelated methods.

In a first aspect, the embodiment of the present disclosure provides atype of workpiece. The workpiece includes the substrate and the polymerthin film that is formed on the substrate. The substrate includes a baseplate, grounding electrodes, and grounding pads. The grounding pads andelectrodes are placed on the same surface of the base plate. Thegrounding electrodes are covered by the polymer thin film, while thegrounding pads remain exposed. The grounding pads are at the edges ofthe base plate. There are multiple grounding electrodes. The groundingelectrodes are spaced apart on the base plate.

In a second aspect, the embodiment of the present disclosure provides atype of carrier platform. The carrier platform is used to carry theworkpiece, as described in the first aspect. The carrier platform ispresented as a flat plate and has a substrate carrying recess. The baseof the substrate carrying recess has at least two jacking holes that runthrough the thickness of the carrier platform. On the surface of thecarrier platform opposite to the substrate carrying recess, there aregrounding ports. The carrier platform also includes carrier electrodeswith at least some of the carrier electrodes placed at the bottom of thegrounding ports and some at the sides of the substrate carrying recess.

In a third aspect, the embodiment of the present disclosure provides atype of poling chamber. The poling chamber is used to polarize theworkpiece on the carrier platform, as stated in the second aspect. Thepoling chamber includes a second Z-elevator and cover. The coverincludes a conductive pad. The second Z-elevator includes a groundingwire. The second Z-elevator is situated below the cover. When thecarrier platform and the workpiece on the carrier platform are at thepreset second position, the second Z-elevator moves up to push thecarrier platform up to come into contact with the cover. The coverexposes the polymer thin film on the carrier platform. The conductivepad of the cover becomes electrically connected with the grounding padsof the workpiece and the carrier electrodes of the carrier platform,simultaneously. The grounding wires of the second Z-elevator come intocontact with the carrier electrodes of the carrier platform.

In a fourth aspect, the embodiment of the present disclosure providesanother type of workpiece to be polarized, which includes: a base plate;an electrode layer formed on a surface of the base place, including aplurality of grounding electrodes and one or more grounding pads, thegrounding pads being located at edges of the base plate, each groundingelectrode being electrically connected to at least one of the groundingpads, the plurality of grounding electrodes being spatially separatefrom each other; and a polymer thin film formed on the base plate over aportion of the electrode layer, the polymer thin film including aplurality of spatially separate thin film areas, each thin film areacovering one of the plurality of grounding electrodes, the thin filmleaving the grounding pads uncovered.

In a fifth aspect, the embodiment of the present disclosure provides apoling apparatus for poling a polymer thin film formed on a work piece,the work piece being disposed on a workpiece carrier, the polingapparatus including: a poling source configured to generate a plasma; aZ-elevator disposed below the poling source and configured to move theworkpiece carrier in a vertical direction, the Z-elevator including aconductive grounding cable which has a portion that is exposed at a topof the Z-elevator; a shadow mask formed of an electrically insulatingmaterial, the shadow mask defining a plurality of openings; one or moreelectrically conductive grounding terminals mounted on an underside ofthe shadow mask, located in a peripheral area of the shadow mask, theshadow mask being disposed above the Z-elevator with the conductivegrounding terminals facing downwardly; and an enclosure configured toenclose the poling source, the Z-elevator and the grounding mechanism.

Compared with existing technology, the embodiment of the presentdisclosure allows polarized polymer thin films to be cut into smallpieces of polarized film, increasing the production efficiency of smallsize polarized polymer thin films. Such poling is achieved through amethod and set up, including a workpiece, a carrier platform, and apoling chamber. The workpiece includes the substrate and the polymerthin film formed on the substrate. The substrate includes a base plate,grounding electrodes, and grounding pads. The grounding pads are at theedges of the base plate. There may be multiple grounding electrodes. Thegrounding electrodes are aligned in an array. The grounding pads andelectrodes are on the same surface. The grounding electrodes are coveredby the polymer thin film, while the grounding pads remain exposed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the working principle of plasma poling of polymerthin films according to an embodiment of the present invention.

FIG. 2 shows the system architecture including key functional modulesfor mass production process for poling thin films in accordance with anembodiment of the present invention.

FIG. 3 is an overview of the process module of the apparatus for polingpolymer thin films in accordance with an embodiment of this invention.

FIG. 4 illustrates further the basic construct of workpiece carrierinside the process module, which is shown in FIG. 3.

FIG. 5 illustrates how grounding of bottom electrode (on workpiece) isimplemented before poling process starts.

FIG. 6 illustrates large area poling source in relation to itssurroundings in the process module in terms of electro-mechanicalintegration.

FIG. 7 shows how the large area poling source is electrically wired byusing arrayed, smaller poling sources.

FIG. 8 is a block diagram showing components of a system for polingpolymer thin films according to an embodiment of the present invention.

FIG. 9 illustrates the principle of direct poling of polymer thin films.

FIG. 10 illustrates a workpiece having a polymer thin films to beprocessed by the poling apparatus according to an embodiment of thepresent invention.

FIG. 11 is a schematic structural diagram of the poling device accordingto another embodiment of the present invention.

FIG. 12 is a schematic structural diagram of the substrate, according tothe embodiment of the present invention.

FIG. 13 is a schematic structural diagram of the carrier platformaccording to the embodiment of the present invention.

FIG. 14 is a schematic structural diagram of the preparation platformaccording to the embodiment of the present invention.

FIG. 15 is a schematic structural diagram of the polarization chamberaccording to the embodiment of the present invention.

FIG. 16 is a schematic structural diagram of the transfer platformaccording to the embodiment of the present invention.

FIG. 17 is a schematic flowchart of the polarization method according toanother embodiment of the present invention.

FIG. 18 illustrates another workpiece having a polymer thin films inselected areas to be processed by the poling apparatus according toanother embodiment of the present invention.

FIGS. 19A and 19B are top and cross-sectional views, respectively, ofthe workpiece and an electrically insulating shadow mask which is to beassembled onto the word piece according to the embodiment of FIG. 18.

FIG. 20 is an overview of the process module of the apparatus forprocessing the workpiece of FIG. 18 in accordance with an embodiment ofthis invention.

FIG. 21A shows the relationship among the scanning poling source, theshadow mask and the workpiece carrier in the process module of FIG. 20.

FIGS. 21B-21F illustrate various positions of the workpiece carrier andthe workpiece before, during and after poling.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is further described in greater detail below withreference to the attached drawings and embodiments. It is understoodthat the specific embodiments described herein are only used to explainthe invention, but not to limit the invention. In addition, it should benoted that, for the convenience of description, only some but not allstructures related to the invention are shown in the drawings.

Before discussing the exemplary embodiments in more detail, it should bementioned that some exemplary embodiments are described as processes ormethods depicted as flowcharts. Although the flowchart describes thesteps as sequential processing, many of the steps can be performed inparallel, concurrently, or simultaneously. In addition, the order of thesteps can be rearranged. The process may be terminated when itsoperation is completed, but may also have additional steps not includedin the drawings. The process may correspond to methods, functions,procedures, subroutines, subprocesses, and so on.

In addition, the terms “first”, “second”, etc., may be used herein todescribe various directions, actions, steps, or elements, etc., itshould be understood that they should not be limited by these terms.These terms are only used to distinguish one direction, action, step, orelement from another direction, action, step, or element. For example,without departing from the scope of the present application, the firstspeed difference may be referred to as the second speed difference, andsimilarly, the second speed difference may be referred to as the firstspeed difference. Both the first speed difference and the second speeddifference are speed differences, but they are not the same speeddifference. The terms “first”, “second”, etc. should not be interpretedas indicating or suggesting relative importance or implicitly indicatingthe number of technical features indicated. Therefore, the featuresdefined as “first” and “second” may explicitly or implicitly include oneor more of the particular features. In the description of the invention,the meaning of “multiple” is at least two, for example, two, three,etc., unless it is clearly and specifically defined otherwise.

Unlike direct poling, plasma poling is advantageous that no depositedconductive electrodes are necessary on the two surfaces of the polymerthin film. When a uniform, dynamically stable layer of dense electricalcharge is formed on the top surface of the polymer thin film, the neededelectrical field is readily maintained to be able to conduct qualitypoling. Although plasma poling is essentially electrodeless, it ispractically useful in actual mass production to build in a bottomelectrode (often a thin conductive film, such as metal or ITO, i.e.indium tin oxide) underneath the polymer thin film. The bottom electrodeso formed serves a few purposes. One such primary purpose is to maintaina stable electrical potential difference between the top of the polymerthin film (in contact of the electrical charge layer) and bottomelectrode by electrically grounding the bottom electrode to theapparatus's physical ground. Connecting the bottom electrode to thephysical ground may lead to a higher electric field for faster and morespatially uniform poling process which is otherwise not achievable if nobottom electrode were grounded.

FIG. 1 shows the basic configuration and principle of a process module(also referred to as a process chamber or poling chamber) 200 for aplasma poling apparatus. Inside an enclosed chamber 201 (for environmentisolation), a workpiece 202 is placed on the substrate pedestal 209. Asshown in FIG. 10, the workpiece 202 includes a PVDF (or its co-polymer)thin film 202A deposited on bottom electrode layer 202B/202D, which isin turn deposited on a glass (or other insulating, or semiconductingmaterials) base plate 202C (the bottom electrode layer and the glassbase plate may be collectively referred to as the substrate of theworkpiece). The bottom electrode layer has an electrode pattern thatincludes an array of multiple of bottom electrodes 202B, multiplegrounding pads 202D that are located along the perimeter of theworkpiece, and wires that connect the bottom electrodes to the groundingpads. Each bottom electrode may correspond to an individual deviceformed by the thin film, and the bottom electrodes may also be referredto as a device array. Each bottom electrodes 202B is electricallyconnected by wires to at least one of the grounding pads 202D. In theillustrated embodiment, all bottom electrodes 202B and all groundingpads 202D are electrically connected together. The thin film 202A coverssubstantially the entire area of the substrate but leaves each groundingpad 202D at least partly uncovered. For clarity, FIG. 10 shows asubstrate of the workpiece without the thin film and a workpiece withthe thin film. In operation, a layer of electric charge (charge cloud)203 is dynamically formed above the PVDF thin film. This layer of chargecontributes largely to generate a strong electric field (typically10⁷˜10⁹ volt/meter) perpendicular to the thin film surface. The electricfield is responsible for polarizing (or poling) the electric dipolesexisting inside the PVDF thin film, and for displacing other existingcharges inside the thin film. The plasma poling process converts thePVDF thin film so that opposite charges are separated and reside almostpermanently near the two separate surfaces of the thin film. Once theconversion completes, the thin film becomes electroactive. For example,piezoelectricity is such an electroactive property that is used of PVDFthin films for pressure sensors and ultrasonic fingerprint sensors.

Referring to FIG. 1 again, continuous supply of electric charge flux isfacilitated by a poling source 204, which includes a plasma source 205and a grid electrode 206. The grid electrode is set at a differentelectrical potential than that of the plasma source. Electric chargesboth positive and negative are first generated by ionizing processinggases inside the plasma source. The like electrical charges (e.g.,electrons, negatively charged ions or molecular species) are thenattracted by the grid electrode (which is set by a grid power supply 207at a slightly higher electrical potential than that of the plasma sourceset by a plasma source power supply 208) and pass the openings of thegrid, eventually reaching a region adjacent to the surface of the thinfilm to dynamically form the charge cloud. In general, the plasma sourcemay be based on a number of gas ionizing mechanisms or implementations.These may include gas discharges excited by DC (direct current), RF(radio frequency), microwave, pulsed DC, X-ray, and possiblecombinations thereof.

For mass production of poling polymer thin films, system architecture ofthe apparatus in accordance with an embodiment of the current inventionis illustrated by FIG. 2. Incoming workpieces (e.g., polymer thin filmsdeposited on glass substrates) are picked up by a front-end robot orother suitable devices 214 from workpiece storage cassettes 215 andsubsequently transferred into the process module 200. The process moduleis where poling operation is carried out, along with other ancillarysubstrate handling and preparation operations before and after theactual poling process. Once the poling process is finished, thefront-end robot reaches inside the process module, picks up theprocessed workpiece, and transfers it back to the workpiece storagecassette. More than one cassette may be featured for productivityreasons. FIG. 2 also shows some exemplary dimensions of the variouscomponents of the system.

The system and process generally include the following features: 1.Consolidate preparation function and processing function into oneprocess module. Preparation is to condition the glass substrate readyfor subsequent processing, which is to polarize (or pole) the polymerthin film. 2. Grounding mechanisms are installed inside the processchamber. This eliminates the need to prepare the substrate with othermodules or robotic mechanisms. 3. An isolation door 212 is provided atthe front of the process module. When the door is open, the front-endrobot picks up the workpiece to be processed from a cassette andtransfers the workpiece into the process module where the workpiececarrier 213 is housed. 4. The workpiece in the carrier will then beraised by a Z-elevator inside the process module to engage withgrounding mechanisms in the module to condition the grounding needed forpoling process. 5. The above procedure is also concurrent with settingthe gap between poling source and the glass substrate by the Z-elevator.6. Poling process is initiated and continues until it is finished. 7.The workpiece in the carrier is then lowered by Z-elevator, while beingdisengaged with the grounding mechanisms at the same time.

Further shown in FIG. 3, inside the process module 200, an X-Y scanningstage 216 drives a large area poling source 204 in horizontal plane tosupply needed charge flux to enable poling over large area workpiece 202(the array of bottom electrodes and the thin film are not shown). Theworkpiece is situated inside a workpiece carrier 213, which can beraised or lowered by a vertically moving Z-elevator 217 controlled by aprecision servo motor. The Z-elevator sets the distance or gap (theprocess gap) between the surface of the workpiece 202 and the bottom ofthe poling source 204 which is an important process parameter duringpoling operation. Although plasma poling is basically electrodeless, itis of advantage to have a bottom electrode 202B (wired to the groundingpads 202D that are located along the perimeter of the workpiece, seealso FIG. 10) connected to a controlled electrical potential referencein mass production. Such potential reference may be the physical groundof the apparatus itself. To facilitate electrical connection between thephysical ground (and monitoring instrument) of the apparatus and thegrounding pads built-in on the circuitry of the workpiece, groundingmechanisms 218, as functional components of the process module 200, areconstructed along the peripheral surrounding the workpiece carrier 213.The grounding mechanisms may include extension damping mechanisms 218A(e.g. extension springing dampers with sliding guides, or otherresilient members), and electrical contacts 218B which are mechanicallyconnected to the extension damping mechanisms, where the electricalcontacts are biased by the extension damping mechanisms downwardly to beable to engage with grounding pads 202D on the workpiece during polingoperation.

Cross-referring to both FIGS. 4 and 5, the workpiece carrier 213 has abuilt-in electrically conducting (e.g. metal) lining 213A as a baseplate supporting the glass substrate 202C. The rest of the carrier 213(the platform) is formed of, e.g., an insulating polymer structure. Thelining 213A has one or more portions 213B that are exposed at the topsurface of the carrier around the recess, at locations (in the top view)adjacent to the grounding pads 202D of the workpiece, so that they willbe electrically coupled to the grounding pads 202D of the workpiece bythe electrical contacts (conductive pads) 218B of the groundingmechanism. In addition, this conductive lining is wired by conductivegrounding cables 219 to the apparatus's physical ground and aninstrument (often an electrometer) 210 (see FIG. 1), which is used tomonitor the poling process. Before and after poling when the workpiececarrier is in a lowered position, the grounding pads 202D around theedges on the workpiece are not electrically connected to the apparatus'sground since the workpiece carrier is not engaged with the groundingmechanisms mounted inside the process module. Now, in order to conditionor prepare the workpiece for actual poling, the workpiece already insidethe carrier 213 is being raised by the Z-elevator (as indicated by theupward arrow) from a lowered position; along its way up, the workpiececaptures and engages with the grounding mechanisms such that theconductive pads (e.g. conductive foam pads) 218B hidden underneath anotherwise insulating cover 218C (of the grounding mechanisms) isgradually brought into electrical contact with the matching groundingpads 202D on the glass substrate (workpiece). In this process, theconductive pads 218B also comes into contact with the exposed liningportion 213B, thereby electrically connecting the lining 213A with thegrounding pads 202D of the workpiece. When the Z-elevator stops at apre-programmed height defining the process gap, grounding from theworkpiece to the apparatus's ground and to the monitoring instrument issecured with the aid of the extension dampers inside individualgrounding mechanisms. Note that in FIGS. 3, 4 and 5, the grounding pads202D are depicted as having a substantial thickness and protruding abovethe rest of the surface of the workpiece 202; this is an exaggerateddepiction, as the actual grounding pads are thin and do not appreciablyprotrude from the workpiece surface. At the pre-set process gap betweenthe poling source and the workpiece, the plasma source and gridelectrode are turned on to carry on the poling process.

The grounding mechanism may include multiple individual mechanismsdisposed at different locations around the workpiece carrier. Forexample, four grounding mechanisms having elongated shapes in the topview may be provided, respectively along the four sides of the workpiececarrier. Alternatively, multiple grounding mechanisms may be disposedalong each side of the grounding mechanisms. The grounding mechanism mayalso be constructed as one piece having a rectangular shape in the topview. In such a case, the cover 218C is a closed frame with an openingthat is slightly smaller than the workpiece, where the inner edges ofthe frame cover one or more (e.g. all) edges of the workpiece but theopening exposes the entire thin film 202A, and the conductive pads 218Bare on the underside of the inner edges of the frame that covers theedges of the workpiece. In all cases, the cover 218C and the conductivepads 218B leave the entire thin film uncovered and exposed to the plasmacloud.

As briefly introduced earlier, in the process module 200, a polingsource 204 supplies needed electric charge flux to dynamically maintaina layer of charge cloud 203 to enable poling the polymer thin film withstrong electric field. FIGS. 6 and 7 show the poling source in moredetails, and illustrates the integration of the poling source with theenclosure 201. The X-Y scanning stage 216 and the poling source 204 aremounted within a liftable top enclosure structure 201A of the processmodule. A cabinet 220 containing the power supplies and control devicesis also mounted on the liftable top enclosure structure 201A. Power tothe plasma source 205 and grid electrode 206 is conducted to the sourcebus and grid bus inside the enclosure via high voltage feedthroughs 221and 222, respectively. For processing large area workpiece (on the meterscale), an X-Y scanning poling source is very helpful to achieve uniformpoling. The large area scanning poling source shown in FIG. 6 isconstructed by arranging multiple smaller poling sources mounted on amounting structure 223, each of which can be considered as a polingsource itself but only covers a much smaller area. As may be required bythe industry to gradually upgrade the size of device substrate, thescanning poling source is readily scalable by an arrayed structure asshown in FIG. 7. The arrayed structure includes multiple poling sourcegroups 224 electrically connected to power supplies in an electricalcircuitry such as that shown in FIG. 7. In the illustrated example,multiple (e.g. 10) individual poling sources (such as 204) form a group224, which are in turn arrayed. Multiple power supplies 207, 208 may beused to supply power to the multiple poling source groups via highvoltage relays. Each grid power supply 207 and plasma source powersupply 208 may be, for example, a −18 kV DC, 60VA power supply. Based onthis arrayed design, the apparatus can be scaled up and processworkpieces of almost any size, from 200 mm silicon wafers, Gen2.5 glass(370×470 mm), Gen6 glass (1850×1500 mm), all the way to Gen10.5 glass(2940×3370 mm), for example.

FIG. 8 is a block diagram showing components of the polymer thin filmpoling system according to an embodiment of the present invention. Thecomponents mentioned above, including the plasma source power supplies208, grid power supplies 207, electrometer 210, and motor controllers225 for the Z-elevator server motor are connected to and controlled by acontroller 226 which may be an industrial computer or programmable logiccontroller. The system also includes a human machine interface 227, datastorage (memory) 228, and analog/digital I/Os 229, also connected to thecontroller.

The preferred embodiment of this invention has proposed an efficientsystem architecture for the disclosed apparatus to process workpiece ina manner that sequential preparation (conditioning) and poling functionsare integrated into one module. This architecture eliminates the needfor separate preparation stations (or modules) dedicated to groundingoperation of the workpiece prior to the poling operation. It in turnreduces apparatus's cost, as well as its footprint, which is a valuablefeature for semiconductor, display and sensor factories.

By adopting modularized, arrayed poling sources, the disclosed apparatusdesign is capable of scaling up in substrate size easily andsystematically. Furthermore, with arrayed sources, effort totroubleshoot large area poling source becomes less and more costeffective, since failed individual poling sources may be easilyidentified and replaced without taking down or discarding the entirelarge area poling source.

The disclosed method of grounding the bottom electrode underneath thepolymer thin film can be easily implemented in mass production. Itenables faster process for poling since the electrical potential of thebottom electrode is prevented from floating up with little control in aplasma inside the process module. Plasma induced potential floating mayoccur if the bottom electrode were not grounded otherwise. The electricfield strength across the surfaces of the polymer thin film isdetermined by the difference of electrical potentials on the twosurfaces. Besides helping with poling speed, the method also enablesuniform poling over large areas because all the bottom electrodes ofdevices laid out over the substrate can be kept at a common electricalpotential.

The above method of grounding is also very important to realize higheryield in mass production with plasma poling. In many cases where activesensing devices are involved, the PVDF thin films need to be fabricatedon top of other active circuitries such as CMOS or TFT (thin filmtransistor) devices. To avoid possible plasma or high voltage damages tothose active devices already built in on the substrate, certainprotective circuitries must be considered in order to carry our polingoperation. During poling process, these protective circuitries must beconnected to the common grounding pads on the substrate which aresubsequently connected to the physical ground of the poling apparatus.

Another embodiment of the invention is described with reference to FIGS.11-17 below. The workpiece and polling chamber themselves in thisembodiment is similar to that in the embodiments of FIGS. 1-10, but thesystem uses a different workpiece transport structure.

Referring to FIG. 11: The first embodiment of the current disclosureprovides a poling system 10 used to polarize a workpiece 15. The polingsystem 10 includes: preparation platform 11, poling chamber 12, transferplatform 13, and carrier platform 14. The poling chamber 12 ispositioned between the preparation platform 11 and the transfer platform13. The preparation platform 11 is used to hold the carrier platform 14before being sent into the poling chamber 12. The carrier platform 14 isused to hold the workpiece 15. The poling chamber 12 polarizes theworkpiece 15 on the carrier platform 14. The transfer platform 13 isused to hold the workpiece 15 after it has been polarized. Specifically,when the carrier platform 14 is transferred to the preparation platform11, the workpiece 15 is placed on to the carrier platform 14. When thecarrier platform 14 and the workpiece 15 are moved into the polingchamber 12, said workpiece 15 is then polymerized in the poling chamber12. Upon completion of polymerization, the carrier platform 14, alongwith the workpiece 15, is moved to the transfer platform 13. The polymerworkpiece 15 is then subsequently removed from the carrier platform 14.

Referring to FIG. 12: The workpiece 15 includes substrate 151 and thepolymer thin film formed on the substrate 151 (not shown in the figure).Preferably, the polymer forms into a thin film in-situ on the substrate151. After the workpiece 15 is polarized, it can be cut into multiplepieces. As multiple regions are polarized simultaneously, the speed ofpolarization is enhanced. The formation of the polymer thin film thattakes place, in-situ, at the surface of the substrate 151, which yieldsa substrate 151 with a polymer thin film attached and ready forpoling—which is the workpiece 15. This is a key difference between knowncurrent technology and this embodiment. The known current technologyinvolves the attachment, via adhesion, of a preformed polymer thin filmto a substrate, followed by poling process. Usually, the preformedpolymer thin film has to be first stretched to certain stress so that itcan be placed on, and adhere to a substrate before poling can takeplace. For the known current technology, the polymer thin film usuallyhas to be thicker than 30 μm, which is not suited for current trendsthat pursue light and thin electronic components. Also, thepiezoelectric inductance devices using such films provide lessresolution due to the thick film. In this embodiment of the presentinvention, the polymer thin film is formed in-situ at the surface of thesubstrate 151 through spin coating, screen printing, and slit coatingtechniques. This allows the formation of very thin polymer thin films,usually kept under 9 μm. The piezoelectric sensing devices using suchin-situ formed polarized polymer thin films provide much betterresolution. This embodiment also can broaden the scope of electroniccomponent designs as thin films of varying thicknesses can be employed.

The polymer thin films may be ferroelectric polymer thin films, such as:polyvinylidene fluoride (PVDF), polyvinylidene fluoridetrifluoroethylene (PVDF-TrFE), polymethyl methacrylate (PMMA), orpolytetrafuoroethylene (TEFLON).

The substrate 151 includes: a base plate 1511, grounding electrodes(bottom electrodes) 1512, and grounding pads 1513. The grounding pads1513 are located at the edges of the base plate 1511. Grounding pads1513 and grounding electrodes 1512 are on the same surface of the baseplate 1511. The grounding electrode 1512 and grounding pad 1513 areelectrically connected. The polymer thin film covers the groundingelectrode 1512, with the grounding pad 1513 remaining exposed. Thesubstrate 151 may be a glass substrate.

There may be multiple grounding electrodes 1512. The groundingelectrodes are aligned in a matrix format on the base plate 1511. Thepolymer thin film is formed in-situ on the surface of the base plate1511, including the grounding electrodes 1512, and the grounding pads1513. The polymer thin film covers the grounding electrodes 1512, butleaves the grounding pads 1513 at least partially exposed. The groundingpads 1513 are electrically connected to the polymer thin film via thegrounding electrodes 1512. The grounding electrodes 1512 may be a sheetor mesh. The shape of the grounding electrode 1512 is consistent withthe shape of each small piece of the workpiece that will be cut from theworkpiece 15 after poling. The electric potential is zero at the polymerthin film and the grounding electrode 1512 when the grounding electrode1512 is grounded.

Referring to FIG. 13: The carrier platform 14 is horizontally flat inshape and has a substrate carrying recess 141 at the top. At the base ofthe substrate carrying recess 141 there are at two openings thatvertically pass through the carrier platform 14 to form the jackingholes 142. On the surface of the carrier platform 14 opposite to that ofthe substrate carrying recess 141, there are grounding ports 143. Thereare also carrier electrodes 144 on the carrier platform 14. Some carrierelectrodes 144 are at the bottom of the grounding ports 143, while someare placed at the sides and top surrounding the substrate carryingrecess 141. It is understood that the placement of carrier electrodes144 at the base of the substrate carrying recess 141 is an option. Thecarrier electrodes 144 at different positions are mutually electricallyconnected. The carrier recess 141 is configured to hold the workpiece15. When the workpiece 15 is placed in the substrate carrying recess141, the top surface of the polymer workpiece 15 is either flush with orhigher than the upper surface of the edge around the substrate carryingrecess 141. The jacking hole 142 is configured for an external device topass through it to elevate the polymer workpiece 15. The grounding port143 is configured for another external device to be inserted into it toground the carrier electrode 144. The grounding port 143 is alsoconfigured for the external device to be inserted to elevate the carrierplatform 14 while grounding the electric circuit. If there are carrierelectrodes 144 placed at the base and at the sides of the substratecarrying recess 141, and the grounding port 143 is made deep enough,then it is understood that the carrier electrode 144 at the base of thesubstrate carrying recess is at the deep end of the grounding port 143.

Referring to FIG. 14: The preparation platform 11 includes the firstconveyor system 112 and the first Z-elevator 111. The first Z-elevator111 is below the first conveyor system 112. The first conveyor system112 moves the carrier platform 14 to a preset first position. Then thefirst Z-elevator 111 passes through the conveyor system 112 and thenthrough the jacking hole 142 of the carrier platform 14. A firstexternal conveyor system places the workpiece 15 on top of the firstZ-elevator 111. The first Z-elevator 111 lowers to place the workpiece15 into the substrate carrying recess 141. Preferably, the preparationplatform 11 includes a first sensor, which is used to detect theposition of the carrier platform 14. As the carrier platform 14 reachesthe preset first position, the first sensor signals the first conveyorsystem 112 to stop the carrier platform 14. The type of the first sensoris not limited. It may be a position limit sensor. It is understood thatthe poling system 10 may also include a controller. The controller iselectrically connected to the first sensor and the first conveyor system112. When the first sensor senses that the carrier platform 14 is at thepreset first position, the control system stops the movement of thefirst conveyor system 112.

The first conveyor system 112 includes multiple rollers (not labeled)spaced apart, with gaps between rollers. As the rollers rotate, theycauses the carrier platform 14 on them to move. The gaps between therollers provide space through which the first Z-elevator 111 passes. Thestructure of the first conveyor system 112 is not limited. For instance,the first conveyor system 112 may alternatively include a conveyor beltwith gaps. As the first Z-elevator 111 lowers, and the polymer workpiece15 is placed into the substrate carrying recess 141, the first conveyorsystem 112 moves and sends the carrier platform 14 into the polingchamber 12.

The first Z-elevator 111 includes first elevating rods 1111 and a firstmotor (not shown). The first motor drives the first elevating rods 1111up and down. There may be multiple first elevating rods 1111. The numberof the first elevating rods 1111 matches the number of the jacking holes142, and the positions of the elevating rods 1111 and the jacking holes142 correspond to each other. The first elevating rods 1111 move up anddown through the corresponding first jacking holes 142. As the firstelevating rods 1111 move up through the first jacking holes 142, thefirst external conveyor system places the workpiece 15 on top of thefirst elevating rods 1111 of the first Z-elevator 111. Preferably, thereare at least 3 sets of first elevating rod 1111 and jacking hole 142, tostably support the workpiece 15 atop the first elevating rods 1111 andto prevent the workpiece from toppling.

Referring to FIG. 15 along with FIG. 11: The poling chamber 12 includesthe poling assembly 121, the second conveyor system 124, the secondZ-elevator 123, and the cover 122. The cover 122 includes a conductivepad (e.g. a conductive foam pad) 1221 and is otherwise insulating. Thesecond Z-elevator 123 includes one or more grounding wires 1231. Thesecond Z-elevator 123 is positioned below the second conveyor system124. The poling assembly 121 is placed above the second conveyor system124. The cover 122 is between the second conveyor system 124 and thepoling assembly 121. The poling assembly 121 is above the cover 122.After the carrier platform 14 is positioned by the second conveyorsystem 124 to a preset second position, the second Z-elevator 123 rises,allowing it to pass through the second conveyor system 124 and to beinserted into the jacking holes 142 of the carrier platform 14. Thiscauses the carrier platform 14 to rise and come into contact with thecover 122. The cover 122 covers the grounding pads 1513 of the workpiece15 and exposes the polymer thin film of workpiece 15. The conductivepads 1221 of the cover 122 simultaneously connect with the groundingpads 1513 of the workpiece 15 and the carrier electrodes 144 on thesides of the substrate carrying recess 141. The grounding wire 1231 ofthe second Z-elevator 123 has a portion that is exposed at the top ofthe second Z-elevator 123 so that it comes into contact with the carrierelectrodes 144 at the bottom of the grounding port 143. Then, the polingassembly 121 polarizes (poles) the polymer film. Upon completion ofpoling, the second Z-elevator 123 lowers, and the workpiece 15 istransported by the second conveyor system 124 onto the transfer platform13. Preferably, the poling chamber 12 includes a second sensor. Thissecond sensor is used to detect the position of the carrier platform 14.When the carrier platform 14 reaches the preset second position, thesecond sensor signals the second conveyor system 124 to stop the carrierplatform 14. The type of the second sensor is not limited; for example,it may be a position limit sensor.

The set-up of the second conveyor 124 may be consistent with that of thefirst conveyor system 112. For example, the second conveyor system 124may include multiple rollers spaced apart, with gaps between rollers.The second conveyor system 124 may alternatively include a conveyor beltwith gaps. The gaps allow the second Z-elevator 123 to pass through.

The second Z-elevator 123 includes second elevating rods (not marked)and a second motor (not shown). The second motor drives the secondelevating rods up and down. There may be multiple second elevating rods.The number of second elevating rods matches the number of groundingports 143 with corresponding positions. When the second elevating rodsmove up, they are inserted into the grounding ports 143, and as thesecond elevating rods move, they move the carrier platform 14 in acorresponding direction. The grounding wire 1231 passes through thesecond elevating rod and is exposed at the end close to the polingassembly 121, while the other end remains grounded. When the secondelevating rod rises, the grounding wire 1231 electrically connects withthe carrier electrodes 144.

The shape of the cover 122 is not limited. The cover 122 allowselectrical connection between the grounding pads 1513 and the carrierelectrodes 144. This allows the grounding electrodes 1512 of theworkpiece 15 on the carrier platform 14 to be grounded through thegrounding pads 1513, the conduction pad 1221, the carrier electrode 144,and the grounding wire 1231; hence, the lower surface of the polymerthin film is grounded. The cover 122 covers the grounding pads 1513 ofthe workpiece 15 and exposes the polymer thin film on the workpiece 15.Through the poling voltage provided evenly by the poling assembly 121,the polymer gets polarized.

The poling assembly 121 includes a mounting device as well as multiplepoling modules. The mounting device and the poling modules may bedissembled and reassembled. Multiple poling modules may be used topolarize multiple regions of the workpiece 15. Damaged poling modulescan easily be replaced, making it convenient for production assembly andmaintenance. The positions of the multiple poling modules correspond tothose of the grounding electrodes 1512, with each module polarizing acorresponding section of the polymer thin film. Preferably, the polingmodules form an array and are aligned with the array of groundingelectrodes 1512. Each poling module polarizes the piece/region ofpolymer thin film associated with the corresponding grounding electrode1512. Rectangular format array is the preferred arrangement for thepoling modules, preferably in the same plane. Each poling moduleincludes high and low voltage terminals. The low voltage terminal ispositioned between the high voltage terminal and the cover 122. The highvoltage terminal is positioned between the mounting device and the lowvoltage terminal. The mounting device is further away from the cover 122and the second Z-elevator 123, as compared to the poling module. The lowvoltage terminal is above the preset second position. The electricpotential at the high voltage terminal is higher than that of the lowvoltage terminal. The high voltage terminal ionizes ionizable gas aroundit to form a plasma. The ionizable gas may be air, nitrogen, argon, orother ionizable gases. The low voltage terminal attracts the chargesfrom the plasma and uniformly redistribute it to regions close to thesurface of the polymer thin film to form a virtual electrode (a layer ofcharge cloud). Through this virtual electrode, a strong electric fieldforms and allows uniform polarization of the polymer thin film. It isunderstood that a poling module may include the high voltage terminal,low voltage terminal, and the ionizable gas. The high voltage terminalcauses the ionization of the ionizable gas, while the low voltageterminal uniformly distributes the charges in the plasma.

The poling system 10 in this embodiment induces ionization of ionizablegas to form a plasma at the high voltage terminal. Concurrently, throughthe low voltage terminal, the charges in the plasma is uniformlydistributes and are drawn towards the surface of the polymer thin filmforming a virtual electrode (a layer of charge cloud) at the surface ofsaid polymer thin film. It is through the strong electric field providedby this virtual electrode that uniform polarization of the polymer thinfilm is achieved. As compared to “direct poling” via the employment of asingle high voltage source, this technology of “indirect poling” usinghigh and low voltage terminals avoids electric breakdowns at thinner andpinhole regions of the polymer thin film. These breakdowns are seen indirect poling and can cause damage to the underlying microelectronicdevices. In addition, indirect poling can uniformly polarize large areasof the polymer thin film surfaces and improve the production first passyield as well as provide means for mass production. Furthermore, theresulting polarized polymer thin film has a stronger piezoelectriceffect and a longer service life.

The electric potential at the high voltage terminal may be provided byan electric potential source. Preferably, arrayed needle electrodes orlinear electrodes are employed at the high voltage terminal. Thedistance between the high and low voltage terminals is larger than thatbetween the low voltage terminal and the carrier platform 14. It isunderstood that the distance between the low voltage terminal and thecarrier platform 14 is the distance present when the carrier platform 14is pushed up by the second Z-elevator 123.

Preferably, the low voltage terminal is a grid electrode or a plateelectrode with through openings. The low voltage terminal determines theelectric potential at the plane of the low voltage terminal; it alsopromotes uniform distribution of the electric field. There are throughopenings on the plate or grid electrode to allow the passage of ions.For example, a plate or grid electrode may be formed by parallel alignedmetal wires. The gaps between the metal wires form the through openings.Preferably, the low voltage terminal is made of grid electrodes, and thepreferred size of each grid is 1-100 mm². With a square grid, each sideof the grid should be 1-10 mm.

Preferably, the gap between the low voltage terminal and the carrierplatform 14 is 1-10 mm. By adjusting the gap distance between the lowvoltage terminal and the carrier platform 14, there is better control ofthe electric field inside the polymer membrane to achieve a strong andstable intra-membrane electric field. As mentioned earlier, the distancebetween the high and low voltage terminals is larger than that betweenthe low voltage terminal and the carrier platform 14. Preferably, thedistance between the high voltage terminal and the carrier platform 14is 1-500 mm. Most preferred is a distance of 300 mm.

Preferably, the poling chamber 12 further includes a first electricpotential controller to control the potential at the high voltageterminal. It is understood that the first electric potential controlleris connected to a potential source. The control of the potential at thehigh voltage terminal is achieved via control of the potential source.Therefore, by controlling the potential source, the potential at thehigh voltage terminal can be adjusted during the poling process, or tobe regulated for different polymer thin films.

Preferably, the poling apparatus further includes a second electricpotential controller to control the potential at the low voltageterminal. This allows the potential at the low voltage terminal to beadjusted at any time during a poling process or to be adjusted to adaptto different polymer thin films. The potential difference between thehigh and low voltage terminals can be controlled via adjustments of thefirst and second electric potential controllers.

Preferably, the potential is 5-50 kV and 0.3-40 kV at the high and lowvoltage terminals, respectively. The stability of the poling processrelies on the potentials at the high and low voltage terminals. It isnoted here that the electric potential at the high voltage terminal hasto be higher than that at the low voltage terminal. It is preferred thatthe potential at the high voltage terminal be 5-30 kV higher than thepotential at the low voltage terminal. For example, if it is 40 kV atthe high voltage terminal, the low voltage terminal may be 12 kV; if itis 30 kV at the high voltage terminal, the low voltage terminal may be10 kV; if it is 20 kV at the high voltage terminal, the low voltageterminal may be 7 kV; if it is 15 kV at the high voltage terminal, thelow voltage terminal may be 5 kV. In a preferred embodiment, thepotentials are 20 kV and 7 kV at the high and low voltage terminals,respectively, which achieves good stability during poling and producespolarized thin films with good properties.

Preferably, in addition, the poling chamber 12 includes a current sensorto measure the current in the polymer thin film. Through the monitoringof the polymer thin film's current, the endpoint of poling can bedetermined. The current sensor may be electrically connected to thegrounding wire 1231. The endpoint of poling may be determined bymonitoring the real-time changes in the film current, such as the changein the slope. Preferably, a control processor (not shown in the figure),included in the polymer thin film poling device, can receive data fromthe current sensor. It is understood that such data collection betweenthe current sensor and the control processor can occur through a wireddata line or through wireless data transmissions such as Bluetooth orWiFi. The control processor can analyze the film current data, andaccurately determine the poling endpoint based on changes in the slopeof the current curve.

It is understood that the poling chamber 12 also includes an enclosureto provide the polymer workpiece 15 an isolated environment. Thisenclosure does not limit the scope of the embodiment of thisapplication. This enclosure may be a box, a case, a barrow, or even aroom. It is understood that the enclosure includes an entrance and anexit, allowing the entrance and exit of the carrier platform 14 and theworkpiece 15. It is understood that the polarized workpiece is theworkpiece 15 after the completing of polarization. Preferably, theconnection between the cover 122 and the enclosure is elastic. When thesecond Z-elevator 123 pushes the carrier platform 14 up, there is nohard contact between the cover 122 and the enclosure. This preventsdamages to the carrier platform and the cover 122. It is understood thatto ensure accurate positioning of the carrier platform 14 as it israised, a position sensor can be employed, or the number of rotations ofthe second motor can be controlled to limit the movement of the secondelevating rod.

Referring to FIG. 16: The transfer platform 13 includes a third conveyorsystem 132 and a third Z-elevator 131. The third Z-elevator 131 is belowthe third conveyor system 132. The carrier platform 14 is moved to apreset third position by the third conveyor system 132. Then, the thirdZ-elevator 131 rises through the third conveyor system 132 and thejacking hole 142, allowing the carrier platform 14 to rise. A secondexternal conveyor system then moves the polarized polymer workpiece 15away. Preferably, the transfer platform 13 includes a third sensor. Thisthird sensor is for sensing the position of the carrier platform 14. Asthe carrier platform reaches the third position, the third sensorsignals the third conveyor system 132 to stop the movement of carrierplatform 14. The type of the third sensor is not limited; it may be aposition limit sensor.

The structure of the third conveyor system 132 may be similar to that ofthe first conveyor system 112. For example, the third conveyor system132 may include multiple rollers spaced apart by gaps, or a conveyorbelt with gaps, through which the second Z-elevator 123 may pass. Afterthe second conveyor system 124 moves the carrier platform 14 partiallyonto the third conveyor system 132, the third conveyor system 132 movesthe carrier platform 14 to a preset third position.

The third Z-elevator 132 includes the third elevating rod 1311 and athird motor (not shown in the figure). The third motor drives the thirdelevating rods 1311 up and down. There may be multiple third elevatingrods 1311. The number and positions of the third elevating rods 1311correspond to those of the jacking holes 142. As the third elevatingrods 1311 moves up through the jacking holes 142 to elevate thepolarized workpiece 15, the second external conveyor system moves thepolarized workpiece 15 away.

To summarize, the poling system 10 of the embodiments of the presentdisclosure includes a preparation platform 11, poling chamber 12,transfer platform 13, and carrier platform 14. The poling chamber 12 ispositioned between the preparation platform 11 and the transfer platform13. The preparation platform 11 is used to stage the carrier platform 14before its entry into the poling chamber 12. The carrier platform 14carries the workpiece 15. The poling chamber 12 is where poling of thepolymer thin film takes place. The transfer platform 13 is used to stagethe polarized workpiece 15. Thus, an automated process of film poling isrealized. The poling assembly 121 includes multiple poling components inarray alignment, allowing the poling system 10 to polarize large piecesof a workpiece 15. The workpiece 15 is electrically grounded as it israised by the second Z-elevator 123. The poling results are good, andthe process is simple.

Referring to FIG. 17: The second embodiment of this application providesa poling method that is based on the first embodiment of thisapplication. This poling method is used to polarize a polymer thin film.This poling method employs the poling system described in the firstembodiment. The workpiece includes the substrate and the polymer thinfilm formed on the substrate. The poling system includes a preparationplatform, poling chamber, transfer platform, and carrier platform. Thepoling method includes:

S1: Placing the carrier platform, ready for entry into the polingchamber, on the preparation platform;

S2: Placing the workpiece on the carrier platform;

S3: Polarizing the polymer thin film of the workpiece on the carrierplatform in the poling chamber after the carrier platform enters thepoling chamber; and

S4: Placing the polarized workpiece on the transfer platform after thecompletion of polarization of the polymer thin film.

In S1 the carrier platform on the preparation platform does not carrythe workpiece.

In S2, the workpiece is placed on the carrier platform after the carrierplatform is moved to the preparation platform.

In S3, the poling chamber includes the poling assembly, second conveyorsystem, second Z-elevator, and cover. The cover includes the conductivepad. The second Z-elevator includes a grounding wire. The secondZ-elevator is below the second conveyor system. The poling assembly isabove the second conveyor system. The cover is between the secondconveyor system and the poling assembly. The carrier platform is aplate. There is a substrate carrying recess on the carrier platform.There are grounding ports on the carrier platform surface that isopposite to the substrate carrying recess. The carrier platform includescarrier electrodes. At least some of the carrier electrodes are placedat the bottom of the grounding port and some on the sides of thesubstrate carrying recess. After the carrier platform enters the polingchamber, the poling of the polymer thin film of the workpiece on thecarrier platform takes place, which includes:

The carrier platform and the workpiece enter the poling chamber and arepositioned at the preset second position.

The second Z-elevator raises the carrier platform and the workpiece,allowing an electrical connection between the workpiece and theconductive pad of the cover, an electrical connection between theconductive pad of the cover and the carrier electrodes of the carrierplatform, and an electrical connection between the carrier electrodesand the grounding wire of the second Z-elevator.

The poling assembly polarizes the polymer thin film on the workpiece.

In S4, after poling is completed, the workpiece and the carrier platformare moved to the transfer platform. Then, the polarized workpiece isremoved from the carrier platform.

Embodiments of the present disclosure provide a poling method, in whichthe poling system includes a preparation platform, poling chamber,transfer platform, and carrier platform. The poling chamber is locatedbetween the preparation platform and the transfer platform. Thepreparation platform is used to stage the carrier platform before itsentry into the poling chamber. The carrier platform carries theworkpiece, and the poling chamber poles the polymer thin film. Thetransfer platform is used to place the polarized polymer workpiece. Thusan automated process of film poling is achieved. The poling assemblyincludes multiple poling modules in array alignment, allowing the polingsystem to polarize large pieces of a workpiece. The workpiece isgrounded as it is raised by the second Z-elevator. The poling resultsare good, and the process is simple.

Compared to existing technology, the embodiments of this disclosureallow polarized polymer thin films to be cut into smaller polarizedfilms, increasing the production efficiency of small size polarizedpolymer thin films. Such poling is achieved through a method and setupthat comprises of a workpiece, carrier platform, and poling chamber. Theworkpiece includes a substrate and the polymer thin film formed on thissubstrate. The substrate includes a base plate, grounding electrodes,and grounding pads. The grounding pads are aligned in an array at theedge of the base plate; there are multiple grounding electrodes. Thegrounding pads and the grounding electrodes are on the same surface ofthe base plate. The polymer thin film covers the grounding electrodeswhile leaving the grounding pads exposed.

Another embodiment of the present invention which uses a built-inelectrically insulating shadow mask in the process module is describedbelow with reference to FIGS. 18-21F. This embodiment provides a polingchamber and related method to implement mass production process forplasma poling on selected areas of polymer thin films over large sizeworkpiece.

As discussed earlier, one method of producing separate active areas onthe substrate is to selectively deposit the polymer thin film on thesubstrate to define the separate active areas without resort tophotolithography and subsequent etch processes; a matching shadow maskof patterned openings is then used to cover the substrate; the activeareas of the thin film are formed by exposing those defined areasthrough the openings to the electrical charge flux in the plasma polingprocess. In a conventional workflow, a shadow mask is assembled on topof the workpiece (having the polymer thin film deposited in selectiveareas) while the workpiece is outside of the process module, and theworkpiece with the mask is then transported into the process module forpoling. After poling, the workpiece with the mask is transported out ofthe process module, and the shadow mask is removed.

In the embodiment described below, a built-in shadow mask, made ofelectrically insulating materials, is provided inside the processmodule, and laid on top of the workpiece before poling starts. Withpatterned openings, the shadow mask allows electrical charge flux to gothrough the openings to pole selected areas of the polymer thin filmwhile blocking the flux from touching undesired areas on the substrate.For devices with active areas larger than 1×1 millimeter in dimensions,this embodiment offers an ideal and lower cost method of mass productionwhere polymer thin film poling process is involved. Using thistechnique, there is no need to assemble the mask with the workpiece anddisassemble them outside the process module.

FIG. 18 schematically illustrates the workpiece 202′ used with thisembodiment. This workpiece 202′ is similar to the workpiece 202 shown inFIG. 10, except that the PVDF or PVDF-TrFE co-polymer thin film 202A′ isa patterned layer, selectively deposited in multiple separate areas onlyto cover the bottom electrodes (grounding electrodes) 202B. In thisexample, 4×4 bottom electrodes form an array, and each bottom electrodeis rectangular in shape. Each area of the patterned thin film layer202A′ may extend slightly beyond the boundary of the correspondingbottom electrode 202B, but the thin film areas 202A′ covering differentbottom electrodes 202B are separate from each other. This patterned thinfilm layer is deposited or coated, for example using selective slitcoating, screen printing, imprint transferring, etc., on the definedareas. After selective coating and proper crystallization of theco-polymer thin film, the workpiece 202A′ is ready for plasma poling.

FIGS. 19A (top view) and 19B (side cross-sectional view) show thestructure of the shadow mask 231 and its relationship to the workpiece202′. The mask is generally plate shaped with openings 231A. In the topview, the openings 231A are shaped and positioned to match the polymerthin film areas (active areas) 202A′ on the workpiece 202′. In practicalimplementations, each mask opening is preferable slightly smaller thanthe corresponding polymer thin film area, but slightly larger than thecorresponding bottom electrode. In the illustrated embodiment, theopenings are rectangular in shape to match the rectangular shape of thethin film areas 202A′. FIG. 19B shows how the mask openings 231 and thethin film areas 202A′ are aligned with each other when the mask and theworkpiece are assembled (but note that the vertical gap shown in FIG.19B is in fact do not exist during poling). During poling process, theelectrical charge flux is in contact with the thin film areas 202A′through the mask openings 231A. In the meantime, the network wiring andthe grounding pads 202D of the bottom electrode layer are blocked fromthe charge flux by the shadow mask 231; this ensures that the bottomelectrode layer is maintained at a stable electric potential (equals tothat of the apparatus's physical ground).

Referring to FIG. 19B, the shadow mask 231 has multiple electricallyconductive grounding terminals 232 attached to the underside of the maskin the peripheral area of the mask. At least some of the groundingterminals 232 are located at positions corresponding to the groundingpads 202D in the peripheral areas of the workpiece 202′. Once the mask231 and workpiece 202′ are assembled inside the process module, thegrounding pads 202D on the workpiece 202′ are in electrical contact withthe grounding terminals 232 of the mask located just above the workpiece202′. Connecting through the grounding terminals 232 on the mask, thegrounding pads 202D on the workpiece 202′ will eventually routeelectrically to the physical ground of the apparatus during the polingprocess. Note that in the example shown in FIG. 19B, the mask 231 has adownward extending side wall 231B along its outer edge, but this isoptional.

For mass production of poling polymer thin films, the systemarchitecture of the apparatus in accordance with this embodiment issimilar to that illustrated in FIG. 2, except that now the processmodule includes the built-in shadow mask. Masking procedure, i.e. theassembly of the shadow mask with the workpiece, is automaticallyachieved as the workpiece is moved to its process position inside theprocess module. After the poling process is finished, the workpiece isautomatically disengaged from the shadow mask as the processed workpieceis moved to its exchange position to be picked up by incoming substratehandling robot.

The structure of the process module 200′ according to this embodiment,shown in FIG. 20, is similar to the process module 200 shown in FIGS.3-5, but the insulating cover 218C with the electrical contacts 218B inthe process module 200 is replaced by the shadow mask 231 with thegrounding terminals 232. The grounding terminals 232 of the mask servethe same function as the electrical contacts 218B, which is toelectrically connect the metal lining 213A inside the workpiece carrier213 with the grounding pads 202D of the workpiece 202′ when the mask 231is engaged with the workpiece during poling. Similar to the electricalcontacts 218B in FIGS. 3 and 5, the grounding terminals 232 may beformed of conductive foam pads. The mask 231 is locate below the polingsource 204 with a gap; preferably, the vertical position of the mask isfine-adjustable to adjust the size of this gap.

Other aspects of the module 200′ are similar to those of the processmodule 200 described earlier. For example, the rest of the groundingmechanisms 218 of the process module 200, e.g. mechanical supportstructure and the extension damping mechanisms 218A (see FIGS. 3 and 5),remain the same or similar in the process module 200′ even though theyare not shown in FIG. 20. The mask 231 is mechanically coupled to theextension damping mechanisms 218A. The structure of the workpiececarrier 213, including the conductive lining 213A, is the same as orsimilar to that shown in FIGS. 3-5. The vertically moving Z-elevator 217shown in FIGS. 3-4, which moves the workpiece carrier 213 in thevertical direction and has built-in conductive grounding cables 219, ispresent in the process module 200′ although not shown in FIG. 20.

FIG. 20 shows multiple holding pins 235 fixed to the process modulewhich pass through multiple through holes of the workpiece carrier, sothat the workpiece carrier can move freely up and down withoutinterference. As described in more detail later, the holding pins 235serve as an exchange device to facilitate the hand-off of the workpiecebetween the workpiece carrier 213 and the front-end glass handlingrobot. FIG. 20 also shows an isolation slit door valve 236 which is notexplicitly shown in FIG. 3.

With reference to FIGS. 21A-21F, the transport and poling processaccording to this embodiment is described. These figures illustrate theinterior of the process module 200′ with the enclosure omitted. As shownin FIG. 21A, before the workpiece is loaded into the process module, theworkpiece carrier 213 is at its home position; the holding pins 235 areall levelled at the workpiece exchange position. In FIG. 21B, aworkpiece 202′ has just been loaded inside the process module, forexample by a front-end glass handling robot (not shown), and sitting onthe holding pins 235; at this point, the front-end robot has alreadyretracted out of the process module and the isolation slit door valve(not shown) has closed. In FIG. 21C, the workpiece carrier 213 is beingraised (by the Z-elevator 217, not shown) to catch the workpiece 202′now still sitting on the holding pins 235. At the next moment as shownin FIG. 21D, the workpiece carrier 213 has been raised further and hasalready picked up the workpiece 202′, leaving the holding pins 235below.

As the workpiece 202′ is held inside the workpiece carrier 213, theycontinue to rise until the workpiece 202′ and the workpiece carrier 213are fully engaged with the shadow mask 231 from underneath (FIG. 21E).Note that at this process position, the top surface of the polymer thinfilm 202A′ of the workpiece 202′ is in very close contact with thebottom surface of the shadow mask 231; meanwhile, the grounding pads202D on the workpiece are in electrical contact with the groundingterminals 232 attached to the shadow mask. The grounding terminalsfurther form electrical contact with the exposed portions 213B of theconductive lining 213A located around the periphery of the workpiececarrier (see also FIGS. 4 and 5), thereby electrically coupling thebottom electrode 202B of the workpiece 202′ to the physical ground ofthe process module. Note that in FIGS. 19B and 21B-21F, the thicknessesof the bottom electrodes 202B, grounding pads 202D, thin film layer202A′, and grounding terminals 232 are exaggerated for purposes ofillustration.

At this position, the poling source is turned on with X-Y scanning, anda very uniform electrical field for poling is established between thetop and bottom surfaces of the polymer thin film 202A′. Poling iscarried out, with an integrated poling circuitry established from theplasma poling source, workpiece under process, all the way to theapparatus ground. After the poling process is completed, the workpiececarrier 213, holding the workpiece 202′, is disengaged with the shadowmask 231 and is lowering in height; before the carrier is lowered to itshome position, the workpiece is stopped by the holding pins to stay atthe exchange position (FIG. 21F). Next, the isolation slit door valveopens, to let in the front-end robot to pick the processed workpiece andreturn it to the storage cassette.

In the illustrated embodiment, the workpiece carrier 213 is a built-inpart of the process module 200′. For example, it may be fixedly mountedon the Z-elevator 217. Note that the holding pins 235 are optional. Forexample, the front-end robot may directly place the workpiece 202′ onthe workpiece carrier 213 when the latter is at the home position,without the use of holding pins. Or, the holding pins 235 may bemoveable vertically, and can lower the workpiece 202′ into the workpiececarrier 213 before the workpiece carrier raises the workpiece up to themask. In another alternative implementation, the workpiece carrier 213is not a built-in part of the process module 200′, but is transported inand out of the process module with the workpiece in it. In other words,the workpiece 202′ is placed into a workpiece carrier 213 outside of theprocess module, and the workpiece carrier 213 with the workpiece 202′ isloaded into the process module onto the Z-elevator by a transportdevice, such as in the embodiment shown in FIG. 11.

To summarize, the embodiment shown in FIGS. 18-21F provides a processmodule with a built-in shadow mask, and related method, to implementselective (i.e., patterned) poling process on polymer thin films onlarge size substrate. The apparatus's system architecture enablesprocessing the workpiece in a manner such that conditioning for poling,masking scheme and poling operation are combined into one integratedoperation. By adopting the shadow mask for patterned (i.e., selective)poling, this embodiment eliminates the need for post-poling patterningoperations, such as photolithography and subsequent chemical wet etch orplasma dry etch of the polymer thin films. This feature alone willresult in substantial cost savings since there are no needs forexpensive equipment for photolithography, wet- or dry-etch. It will alsoenable more environmental friendly operations in mass production becausemuch less chemicals are consumed.

Increasingly, electroactive polymer-based sensing materials are findingvaluable applications for human-machine interface and biometrics; thecharacteristic size of those sensors (e.g., touch, audio, temperature,infrared, pressure and fingerprint) is of the scale from millimeters tocentimeters. Therefore, using a lower cost shadow mask, instead ofhigher cost photolithography, to implement patterned poling for sensorfabrications is an ideal method to meet the growing demands technicallyand economically.

What has been described and illustrated herein is a preferred embodimentof the disclosure along with the explanation of the principle of thetechnology used. It is to be understood that the embodiment in thisdisclosure is not limited to the technical solutions of the specificcombination of the technical features described herein. The disclosureis capable of other embodiments that utilize equivalent technicalfeatures in varying combinations and of being practiced and carried outin various ways. For example, the technical solutions formed throughadjustment and substitution of the techniques with similar features ofthe techniques disclosed (not limited to) in this disclosure.

Note that the embodiments presented herein are only preferredembodiments of the inventions and the applied technical principles.Those skilled in the art will understand that the present invention isnot limited to the specific embodiments described herein, and thoseskilled in the art can make various noticeable changes, adjustments, andsubstitutions without departing from the scope of the invention.Although an exemplary embodiment described the invention in detail, itdoes not limit the invention, and there may be other additionalembodiments within the scope of the invention, as defined by theappended claims.

What is claimed is:
 1. A poling apparatus for poling a polymer thin filmformed on a work piece, the work piece being disposed on a workpiececarrier, the poling apparatus comprising: a poling source configured togenerate a plasma; a Z-elevator disposed below the poling source andconfigured to move the workpiece carrier in a vertical direction, theZ-elevator including a conductive grounding cable which has a portionthat is exposed at a top of the Z-elevator; a shadow mask formed of anelectrically insulating material, the shadow mask defining a pluralityof openings; one or more electrically conductive grounding terminalsmounted on an underside of the shadow mask, located in a peripheral areaof the shadow mask, the shadow mask being disposed above the Z-elevatorwith the conductive grounding terminals facing downwardly; and anenclosure configured to enclose the poling source, the Z-elevator andthe grounding mechanism.
 2. The poling apparatus of claim 1, furthercomprising: one or more resilient dampers, wherein the shadow mask ismechanically connected to the resilient dampers to move in a verticaldirection and is biased downwardly by the resilient dampers.
 3. Thepoling apparatus of claim 1, wherein the poling source includes: aplasma source configured to generate a plasma by ionizing a processinggas; and a grid electrode disposed below the plasma source, the gridelectrode having through openings configured to pass charged particlesof the plasma.
 4. The poling apparatus of claim 1, wherein eachgrounding terminal is a foam pad.
 5. The poling apparatus of claim 1,wherein the enclosure includes a liftable top, and wherein the polingsource is mounted on the liftable top.
 6. The poling apparatus of claim1, further comprising an X-Y scanning stage affixed to the enclosure,wherein the poling source is mounted on the X-Y scanning stage, andwherein the X-Y scanning stage is configured to move the poling sourcein a horizontal direction.
 7. The poling apparatus of claim 1, furthercomprising a plurality of rollers spaced apart from each other with gapsin between, wherein the Z-elevator includes a plurality of elevatingrods configured to move in a vertical direction passing through thegaps, and wherein the portion of the conductive grounding cable isexposed at a top of one of the elevating rods.
 8. The poling apparatusof claim 1, further comprising the workpiece carrier, which includes: aplatform having a first surface and a second surface opposite to eachother, the first surface defining a recess configured to carry theworkpiece, the second surface defining a plurality of grounding ports;and an electrode formed on the platform, including a plurality of firstelectrode portions exposed in a peripheral area of the first surface ofthe platform around the recess, and at least one second electrodeportion disposed on a bottom of at least one of the grounding ports,wherein the plurality of first electrode portions and the at least onesecond electrode portion are electrically connected to each other. 9.The poling apparatus of claim 8, wherein the Z-elevator is configured tobe inserted into the grounding ports of the workpiece carrier, andwherein the exposed portion of the conductive grounding cable of theZ-elevator is configured to electrically contact the second electrodeportion of the workpiece carrier that is disposed on the bottom of theat least one of the grounding ports.
 10. The poling apparatus of claim8, further comprising: a plurality of pins disposed vertically below theshadow mask; wherein the workpiece carrier defines a plurality ofthrough holes, and the plurality of pins pass through the plurality ofthrough holes.
 11. The poling apparatus of claim 8, further comprisingthe workpiece disposed in the recess of the workpiece carrier, theworkpiece including: a base plate; an electrode layer formed on asurface of the base place, including a plurality of grounding electrodesand one or more grounding pads, the grounding pads being located atedges of the base plate, each grounding electrode being electricallyconnected to at least one of the grounding pads, the plurality ofgrounding electrodes being spatially separate from each other; and apolymer thin film formed on the base plate over a portion of theelectrode layer, the polymer thin film including a plurality ofspatially separate thin film areas, each thin film area covering one ofthe plurality of grounding electrodes, the thin film leaving thegrounding pads uncovered, wherein the openings of the shadow mask haveshapes and positions that match shapes and positions of the separatethin film areas on the workpiece.
 12. The poling apparatus of claim 11,wherein when the Z-elevator moves the workpiece carrier to a predefinedvertical position, each of the plurality of thin film areas of theworkpiece is aligned with and exposed through one of the openings of theshadow mask, and each grounding terminal on the shadow mask isconfigured to electrically contact both one or more of the groundingpads of the workpiece and one or more of the first electrode portions ofthe workpiece carrier.
 13. The poling apparatus of claim 11, wherein theplurality of grounding electrodes form an array; and wherein the polingsource includes a plurality of poling modules forming an array, eachpoling modules being located above a grounding electrode of theworkpiece.